1. Field of the Invention
The present invention relates generally to a steering effort sensor for discriminating between steering and non-steering periods and more specifically to an improved sensor arrangement which provides a positive drive connection between the steering wheel and the steering gear.
2. Description of the Prior Art
In one previously proposed sensor arrangement upper and lower sections of a steering shaft are interconnected by a torsion bar and a switch is provided which is closed upon a given amount of relative displacement between the two sections. However, this arrangement has suffered from a loss of torsional rigidity in the steering shaft and and has required that the components constituting the switch mechanism be produced within very close tolerances. A full disclosure of this arrangement may be found in Japanese Patent application Provisional Publication No. Sho 50-160921.
Further examples of previously proposed sensor arrangements may be found in:
(a) Japanese Patent Application Provisional Publication No. Sho 54-3735, which discloses an arrangement wherein a sensor device is disposed within the steering which per se, so as to be interconnected between an outer shell and an inner frame thereof;
(b) Japanese Patent Application Provisional Publication No. Sho 54-6246 which discloses an arrangement wherein the steering wheel is connected to the steering column through an elastomeric bush and a strain gauge is mounted on the steering wheel and connected to the steering shaft downstream of the bush via a suitable bracket;
(c) Japanese Patent Application Provisional Publication No. Sho 55-17228 which discloses an arrangement wherein the sensor is operatively disposed in one of the steering wheel spokes and the remaining spokes are either connected to the steering shaft through springs or elastomeric members so as to permit sufficient movement of the wheel with respect to the steering shaft; and
(d) Japanese Patent Application Provisional Publication No. Sho 55-44013 which discloses a strain gauge operatively connected to the steering shaft to detect the torque applied thereto.
However, all of these have either required overly precise production, have lacked torsional rigidity have been susceptible to changes in ambient temperature.